1. Field of the Disclosure
This disclosure relates to compositions that provide long lasting hydrophobic coatings with high water contact angles for automotive surfaces, in which the hydrophobic automotive surfaces possess self-cleaning functions, e.g., water and dirt repellency. This disclosure also relates to methods for treating automotive surfaces and to automotive surfaces coated with the compositions.
2. Discussion of the Background Art
Car owners have a long-standing desired to provide their automobiles with a beautiful, shiny appearance, and to protect the underlying paint from environmental damage such as mud, water spots, and the effects of the sun. Over the years, car owners have come to prefer waxes to protect and beautify the exterior painted surfaces of their vehicles because wax finishes are typically more durable than finishes provided by wax-free products, e.g., greases or oils.
The wettability of exterior automotive surfaces is an important property for car owners. Wettability is governed by both the chemical composition and geometrical microstructure of the automotive surface. For car owners, a hydrophobic surface that affords water beading is highly desired.
A characteristic of a hydrophobic surface is that water forms spherical droplets immediately when dropping on the surface. This is referred to as water beading. Such a hydrophobic surface possesses a self-cleaning function. For example, droplets formed on an automotive surface carry dust away after rolling off the automotive surface. This hydrophobic phenomenon is caused by the low surface tension of the surface.
When a liquid drops on a surface of an object, an angle is then formed between the surface and the tangent line of the drop, called contact angle θ. When the tension in the gas-solid interface (also called solid surface energy) is high, the contact angle tends to be low, which means the surface easily gets wet. A contact angle of 0 degrees indicates that water spreads over and becomes a film on the surface so that the surface would completely get wet. On the contrary, if the tension in the gas-solid interface is low, the contact angle tends to be high, indicating that the surface does not easily get wet. Therefore, a contact angle of 180 degrees means that the liquid forms spherical droplets and cannot wet the surface at all.
Currently, hydrophobic automotive surfaces with high water contact angles are arousing interest because these hydrophobic surfaces can be self-cleaning based on their water and dirt repellency. These self-cleaning automotive surfaces offer a high potential for consumers to save on cleaning and other maintenance costs, and also are good for the ecobalance, since cleaning chemicals no longer pollute the environment and since energy is saved by reducing or eliminating maintenance cycles.
There is a need to develop hydrophobic coatings with high water contact angles for automotive surfaces, in which the hydrophobic automotive surfaces possess self-cleaning functions, e.g., water and dirt repellency.
The present disclosure provides many advantages, which shall become apparent as described below.